The present invention relates to high frequency charge pump and integrator circuit capable of translating input pulses on two input lines to an output current related to the input information.
High frequency charge pumps capable of operating at frequencies of 50 megahertz or higher are difficult to design due to stray capacitance associated with the discrete components required in many applications and with the use of integrated PNP transistors in the circuit path. PNP transistors as manufactured at the present time exhibit poor high frequency characteristics.
One type of charge pump uses a tri state gate approach with an external series resistor to determine the charge and discharge currents driving into an active filter. The latter approach provides some improvement over the use of PNP transistors but also sacrifices high frequency performance due to the stray capacitance associated with discrete resistors. Thus, in order to achieve improved speed in a charge pump/integrator circuit it is necessary to develop a circuit which eliminates both PNP transistors and external resistors from the signal path.